Efficiency of using elemental sulfur and sulfuric acid for reclamation of mixed soda -saline soils of the foothill plain of southeastern Kazakhstan

The article presents the results of field studies conducted in the foothill plain of southeastern Kazakhstan in the subzone of light gray soils. Here, on the territory of peasant farms, heavy loamy semihydromorphic solonetz soils of pure soda and mixed soda salinity with increased alkalinity (pH 9.0-10.0) are widespread in the form of spots in microdepressions. Despite their strong solonetzic nature and poor water-physical properties, they are annually subjected to all types of agricultural practices. However, due to the low yield on the noted spots, significant material resources are depreciated. Phosphogypsum, which is a waste product, is still used for their melioration. It is most effective on chloride-sulphate and sulphate-chloride solonetz soils, and is generally ineffective on soda soils. In recent years, in the Republic, due to the accumulation of a huge amount of sulphur, it has been tested as an ameliorant under conditions of only a model experiment. Therefore, the purpose of our research was to determine the comparative melioration efficiency of elemental sulphur with more promising types of ameliorants and to test it in real production conditions. The results of the experiments showed that among the ameliorants, sulfuric acid was more effective than other ameliorants only in terms of the speed and intensity of interaction and in terms of alfalfa productivity (193.20 c/ha per year). However, after a three-year study, the concentrations of carbonate and hydrocarbonate ions in the soil solution were gradually restored. In terms of the duration of the ameliorative effect and alfalfa productivity, the incubation of elemental sulfur was the most effective. Its use made it possible to reduce the very strongly alkaline environment of the studied soils to slightly alkaline (pH 7.8 in the 0-20 cm layer) and completely neutralize soda (CO 3 2 - in the 0-60 cm thickness 0.00 mg-eq). In addition, as a result of long-term sulfur incubation and alfalfa cultivation, the studied soil becomes non-alkaline and slightly saline in the thickness of 0-40 cm, which in the end allowed to obtain a yield of green mass of alfalfa (193.20 c/ha), not inferior to the variant with sulfuric acid.